The disclosure of Japanese Patent Application No. 2003-403667 filed on Dec. 2, 2003, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a hybrid drive unit that can be mounted in a vehicle, and a vehicle in which this hybrid drive unit is mounted. More particularly, the invention relates to a hybrid drive unit having a transfer that distributes driving force to front and rear wheels of a vehicle, and a vehicle provided with the same hybrid drive unit.
2. Description of the Related Art
A front-engine rear-drive (FR) hybrid vehicle includes a hybrid drive unit which is mounted to the rear of the engine and which acts as a transmission.
The hybrid drive unit includes a tubular shaped transmission case (case member) that extends in a front-rear direction, as well as an input shaft, an output shaft, and a hybrid mechanism that are housed within the transmission case. A driving force that is transmitted to the input shaft from an internal combustion engine is changed by the hybrid mechanism and then transmitted to the output shaft. The driving force is then transmitted from the output shaft to the rear wheels via a differential.
When the above described hybrid drive unit is applied to a four-wheel drive vehicle (refer, for example, to Japanese Patent Laid-Open No. Hei. 10-2241), a transfer is provided in the transmission case and the driving force is transmitted to the output shaft via the hybrid mechanism. The transfer functions so as to distribute the driving force to the front and rear wheels.
The above described hybrid drive unit houses both the hybrid mechanism and the transfer within the transmission case, and the utilized hybrid mechanism has at least one electric motor. The electric motor and the transfer are comparatively heavy structural members among the structural members included within the hybrid drive unit (hereinafter referred to as “heavy structural members”).
The above described hybrid drive unit may be mounted such that a second mounting portion at a front end of the transmission case is fixed to the internal combustion engine and a first mounting portion at a rear end of the transmission case is fixed to a vehicle body. As a result, the heavy structural members, namely, the electric motor and the transfer, are positioned between the first and the second mounting portions. However, if this configuration is adopted, resonance is generated by the frequency of vibrations caused by the explosion strokes of the internal combustion engine overlapping with the frequency of bending vibration of the overall hybrid drive unit. Accordingly, the vibrations are amplified and transmitted to the vehicle body, whereby the driver's drive feeling is detrimentally affected.